Re: [Xen-devel] [PATCH 08/15] xen/x86: p2m: Use typesafe gfn for the P2M callbacks get_entry and set_entry

[Julien Grall]

Hi Andrew,

On 09/13/2017 07:22 PM, Andrew Cooper wrote:
On 13/09/2017 18:59, Julien Grall wrote:
diff --git a/xen/arch/x86/mm/p2m-pt.c b/xen/arch/x86/mm/p2m-pt.c
index 0e63d6ed11..57878b1886 100644
--- a/xen/arch/x86/mm/p2m-pt.c
+++ b/xen/arch/x86/mm/p2m-pt.c
@@ -479,12 +479,13 @@ int p2m_pt_handle_deferred_changes(uint64_t gpa)
  
  /* Returns: 0 for success, -errno for failure */
  static int
-p2m_pt_set_entry(struct p2m_domain *p2m, unsigned long gfn, mfn_t mfn,
+p2m_pt_set_entry(struct p2m_domain *p2m, gfn_t gfn_t, mfn_t mfn,
                   unsigned int page_order, p2m_type_t p2mt, p2m_access_t p2ma,
                   int sve)
  {
      /* XXX -- this might be able to be faster iff current->domain == d */
      void *table;
+    unsigned long gfn = gfn_x(gfn_t);
      unsigned long i, gfn_remainder = gfn;
      l1_pgentry_t *p2m_entry, entry_content;
      /* Intermediate table to free if we're replacing it with a superpage. */
@@ -731,11 +732,12 @@ p2m_pt_set_entry(struct p2m_domain *p2m, unsigned long 
gfn, mfn_t mfn,
  }
  
  static mfn_t
-p2m_pt_get_entry(struct p2m_domain *p2m, unsigned long gfn,
+p2m_pt_get_entry(struct p2m_domain *p2m, gfn_t gfn_t,
                   p2m_type_t *t, p2m_access_t *a, p2m_query_t q,
                   unsigned int *page_order, bool_t *sve)
  {
      mfn_t mfn;
+    unsigned long gfn = gfn_x(gfn_t);

These two are rather risky, because you shadow the gfn_t type with a
variable named gfn_t.  I know its ugly, but how about just gfn_ ?

I can do that. Hopefully in the future both functions will be fully 
typesafe, so gfn_ will completely disappear.

Cheers,

--
Julien Grall

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